Display device and control circuit therefor

ABSTRACT

A display device is formed by a glow discharge lamp and has circuit means connected to the lamp for applying thereto selected pulses of either positive or negative polarity for a predetermined time interval, after which the polarity is reversed. During application of pulses of one polarity, an electrode, which is fashioned to be part of the display device will be illuminated and when the other polarity is applied the other electrode, which is fashioned to be another part of the display device, will be illuminated. This will alternately visably illuminate the independent electrodes of the discharge lamp to produce a desired display effect.

United States Patent [191 Quenelle 1 Dec. 10, 1974 [54] DISPLAY DEVICE AND CONTROL CIRCUIT 3,440,489 4/1969 Davidson et a1. 331/113 R H O 3,530,501 9/1970 Van Benschoten 315/272 [75] Inventor: Robert C. Quenelle, Stanford, Calif. Primary ExammerJohn Kominski Asslgneei 1M5 Corporation, q q Attorney, Agent, or Firm-Olson, Trexler, Wolters,

Bushnell & Fosse, Ltd.

[22] Filed: Sept. 17, 1973 [21] Appl. No.: 397,799 [57] ABSTRACT Related US. Application Data A display device is formed by a glow discharge lamp [63] Continuation of Ser. No. 221,247, Jan. 27, 1972, and has circuit means connected to the p for P abandoned, plying thereto selected pulses of either positive or negative polarity for a predetermined time interval, after [52] US. Cl 315/200 A, 313/210, 313/216, which the polarity is reversed. During application of 315/209, 315/272, 340/340, 340/344 pulses of one polarity, an electrode, which is fashioned [51] Int. C1. H05b 37/02 to be p r f h i pl y evice will be illuminated and [581 Field of Search 315/200 ,A, 209, 272; h n the other p y is pp the other electrode, 340/340, 334, 343, 344; 321/45; 313/210, which is fashioned to be another part of the display 216; 307/305; 331/113 device, will be illuminated. This will alternately visably illuminate the independent electrodes of the discharge [56] References Cited lamp to produce a desired display effect.

UNITED STATES PATENTS 11 Claims, 3 Drawing Figures 1,897,473 2/1933 Friedrichsen 313/216 DISPLAY DEVICE AND CONTROL CIRCUIT THEREFOR This is a continuation application of application Ser. No. 221,247, filed .Ian. 27, 1972, now abandoned.

BACKGROUND oF THE INVENTION This invention relates generally to a display device and control circuit therefor, and more particularly to a glow discharge lamp having independent electrodes thereof visably-energizable upon application of voltage of a given polarity.

Glow discharge lamps are well-known in the art and are generally provided with a pair of electrodes to which a voltage of a given polarity may be impressed. With a neon filled lamp the electrode which has the negative voltage will glow upon reaching a voltage level sufficient to cause discharge current to flow within the lamp. If the other electrode is to be visably energized, the polarity need only be reversed to apply negative voltage to that electrode. This arrangement is'relatively useful in forming display apparatus such as signs or decoration-type devices, etc., and merely by sequentially reversing the voltage applied to the desired electrodes can'the desired visual effect be obtained.

Display lights for advertising, or the like, are relatively large and expensive and, many times, require the use of expensive transformers to produce the high voltage necessary for their operation. Furthermore, these types of display lights and their power circuitry are large and do not lend themselves readily to portability.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide an improved control circuit to control the operation of a glow discharge lamp which circuit is simple and inexpensive to manufacture and efficient and reliable in operation.

Another object of this invention is to provide a control circuit for a glow discharge lamp of the type which has independent electrodes alternately energized to give a desired visual effect.

Still another object of this invention is to provide an improved display device and control circuit therefor which is small in size and light in weight and thereby readily portable.

Briefly, the display lamp is a glow discharge device and the control circuit will provide selective illuminatioh of the electrodes of the two-electrodes within the lamp. The principle utilized is that at any one instant of time, only one of the electrodes of the lamp is illuminated while the other is not. For example, whichever electrode in a neon-filled flow discharge lamp happens to be negative with respect to the other will be the electrode which produces a visual glow. Therefore, by controlling the polarity of voltage applied to these electrodes can the visual display be controlled.

One method set forth herein of controlling the polarity of the voltage applied to a glow discharge lamp involves changing alternating current to direct current.

This can be accomplished in several ways, as for exama negative voltage to the other terminal and during the next instant the half-wave rectifier will apply the reverse polarities to the respective terminals. A controlling circuit is provided to select a desired polarity by allowing current to pass through the respective rectifiers.

Another method to control energization of the respective electrodes within a glow discharge lamp is one which utilizes a triac. A triac is a bidirectional switching device, similar to two silicon controlled rectifiers connected back-to-back, with a control electrode to effect conduction of the triac of one polarity or the other depending on the control signal applied thereto. The triac is then operated only on the desired half cycle to provide the proper electrode illumination. To achieve this polarity control, an independent oscillator circuit arrangement is utilized to trigger the triac, this oscillator operating very close to the line frequency of the alternating current voltage. The triac is triggered on opposite half-waves as a function of the beat-frequency between the line frequency and the frequency of the independent oscillator. In effect, the independent oscillator produces trigger pulses which sweep across the line voltage waveform to trigger the triac at varying points on the applied voltage curve. In the preferred embodiment, the oscillator takes the form of a free running multivibrator which is connected to a variable voltage source used to control the rate of oscillation thereof in accordance with the voltages received from the input AC line.

Other objects, features and advantages of this invention will be more fully realized and understood from the following detailed description when taken in conjunction with the accompanying drawings wherein like reference numerals throughout the various views of the drawings are intended to designate the similar elements or components.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Reference is first made to FIG. I which shows a display device designated generally by reference numeral 13. The display device 13 is fashioned somewhat like a standard light bulb and has a threaded electrical contact 6 and a center electrical contact 7 at the lower exterior part thereof. The contacts 6 and 7 are connected to the internal electrodes 18 and 20 via electrical leads 4 and 5, respectively. The electrical leads 4 and 5 also serve as support means for the electrodes 18 and 20 so that they are held spaced apart a predetermined distance and do not touch one another. Here the electrode 18 is a ring and is provided-with indicia DRINK BEER while the electrode 20 is a representation of a beer can. When the display device 13 is connected to its control circuit it is merely threaded into a standard light bulb socket. Therefore, a single control circuit can be used to operate display devices with many different kinds of display patterns therein as well as different kinds of indicia.

Referring now to FIG. 2, a control circuit constructed in accordance with the principles of this invention is designated generally by reference numeral 10. The control circuit controls operation of a display unit 12 of any desired configuration. The display unit 12, however, is of the type which incorporates a glow discharge lamp 13a energizable by a pair of power lines 14 and 16 over which alternating current voltage is applied. In the usual manner, glow discharge lamps of the type intended to be used will have a pair of electrodes 18a and 20a thereof energized such that one of the electrodes will produce a visual energization. For example, if the glow discharge lamp is neon filled, the electrode which is negative with respect to the other willl glow. When alternating voltage is applied across the lamp 13, the rapid alternation of the 60-cycle frequency will give the appearance of having both the electrodes 18 and 20 simultaneously energized. However, if the alternating voltage is divided up into blocks of pulses, one block being a series of positive pulses and the next block being a series of negative pulses, then it would appear that visual energization of the electrodes switches from one to the other. This visual switching back and forth between electrodes will occur at a rate much slower than 60 cycles per second. A current limiting resistor 22 is connected in series with the lamp 13a, and it may be a discrete element or it may be incorporated as an integral part of the lamp as desired.

Most advantageously, the control circuit 10 includes a pair of diodes 24 and 26 connected in parallel one with the other and of opposite conductivity, the diode 24 having its anode connected to line 14 while diode 26 has its cathode connected to line 14. The opposite conductivity characteristic of the diodes will determine the polarity of the pulses passing through the control circuit 10. The diodes 24 and 26 are connected in series with suitable switching means 28 and 30, respectively, they being either mechanical or electronic switching devices as desired. For example, the switching means 28 and 30 can be fast acting electromechanical contacts of a relay or the like or they can be electronic switching devices such as transistors or silicon controlled rectifiers or the like. Furthermore, it will be understood that the diode and switch arrangement can be replaced by a single silicon controlled rectifier in each leg of the circuit. A polarity control circuit 32 has output means thereof connected to the switches 28 and 30 to control closure thereof. For example, when switch 28 is closed, it being understood that the switch 30 remains open, positive pulses will be applied to the electrode 18a and negative pulses to electrode 20a causing a glow discharge at electrode 200. On the other hand, when switch 30 is closed, diode 26 is rendered conductive and negative pulses be applied to electrode 18 and positive pulses to electrode 20a thereby causing a glow discharge at electrode 18a The rate at which the switches 28 and 30 are alternately closed will determine the rate at which the electrodes 18a and 20a will alternately be illuminated.

Referring now to FIG. 3, an alternate form of this invention is illustrated.'Here the display unit 12 is arranged for connection to a pair of power receiving lines 40 and 42 and alternating current voltage is controlled in response to energization of a triac 44 connected in series therewith. The triac 44 has a control electrode 46 for receiving energizing signals from an oscillator circuit, here illustrated as a free running multivibrator circuit 48. Output pulses from the multivibrator circuit 48 are delivered through a capacitor 50 to effect energization of the triac 44. If both electrodes 18a and 20a of the glow discharge lamp 13a are to be energized simultaneously, a bypass switch 52 is provided to shunt the triac 44 and render it inoperative in the circuit.

While a free running multivibrator 48 is illustrated herein as the oscillator circuit it will be understood that any suitable oscillating circuit means can be used to effect the desired result as disclosed herein. The multivibrator circuit 48 includes a pair of transistors 56 and 58 having their collector emitter electrodes connected in series with load resistors 60 and 62, respectively. The transistor 58 has the output electrode, here it being the collector electrode, connected to the capacitor 50 so that voltage pulses are applied to the control electrode 46. The proper frequency of operation of the multivibrator 48 is obtained by selection of the RC time constant of a cross coupling network of resistors 64 and 66 and capacitors 68 and 70. Resistor 64 and capacitor 68 develop an output pulse from transistor 56 and deliver it to the'base electrode of transistor 58 and, in like manner, output pulses from transistor 58 are delivered via the resistor 66 and capacitor 70 to the base electrode of transistor 56. Therefore, transistors 56 and 58 alternately are rendered conductive and nonconductive as a free running multivibrator.

Power is applied to the free running multivibrator circuit 48 by a series connected voltage divider network 72 which has a diode 74 and series resistors 76 and 78 together with a potentiometer 80 connected in series with a charging capacitor 82. Therefore, each time line 40 goes positive, a positive pulse will be applied through the diode 74 and charge capacitor 82 in accordance with the RC time constant of this network.

To maintain the voltage divider network 72, which acts as a power supply for the multivibrator circuit 48, at a constant voltage level, a neon lamp, similar to a NIB-2, or its equivalent, is connected at the juncture of resistors 76 and 78 and functions as a voltage regulator for line voltage variations. That is, because of the nature of the neon lamp, it being rendered conductive at a predetermined voltage value and maintaining that current value regardless of variations in the voltage applied thereto, the voltage on capacitor 82 is substantially regulated in accordance with the setting of potentiometer 80. The circuit of FIG. 3 is a phase sensitive circuit arrangement with the triac 44 operated only on the desired half cycles to provide the desired polarity on one or the other of the electrodes 18a or 20a. The multivibrator circuit 48 is operated at a frequency close to the line frequency, i.e., 60 Hertz or so, and is varied only slightly therefrom by the setting of potentiometer 80. The triac 44 is triggered on opposite half cycles in response to a difference frequency between the line frequency and the frequency of the oscillator 48. In effect, the output of the multivibrator circuit 48 is independent and produces trigger pulses which sweep across the line frequency by adjusting the potentiometer 80. This will vary the point on the voltage curve at which the triac is rendered conductive. The triac can be rendered conductive on either positive cycles to energize one of the electrodes 18a or 20a or be rendered conductive on negative cycles to energize the other of the electrodes desired. This being determined by the output pulse from the multivibrator circuit 48.

What has been described is a simple and efficient display device and control circuit for alternately energizing electrodes within the display device. The display device can be used as a portable advertising sign or as a portable decorative device, or the like. Although only one display device and two circuits are illustrated herein it will be understood that variations and modifications of this invention may be effected without departing from the spirit and scope of the novel concepts disclosed and claimed herein.

The invention is claimed as follows:

1. A control circuit for a glow discharge lamp having independent electrodes to be illuminated upon application thereto of a voltage of a given polarity comprising; circuit means connected to the glow discharge lamp for receiving and alternating current voltage and controlling which polarity of voltage of the alternating current voltage is to be applied to said glow discharge lamp, and a current control circuit connected to said circuit means and in circuit with the glow discharge lamp to control operation of said circuit means to apply to said electrodes a series of voltage pulses of a first polarity for a first time interval and then apply a series of voltage pulses of opposite polarity for a second time interval, thereby alternately visibly illuminating the electrodes of the glow discharge lamp.

2. The control circuit of claim 1, wherein said current control circuit includes polarity selecting means to effect current conduction of a plurality of pulses of said first polarity and then current conduction of a plurality of pulses of said opposite polarity.

3. The control circuit of claim 1 wherein said current control circuit includes first and second diodes connected in parallel and arranged for opposite conductivity, first and second switch means connected in series with said first and second diodes respectively, and polarity control circuit means connected to said first and second switch means alternates to close said-first and second switch means thereby allowing passage of pulses of one polarity and then passage of pulses of another polarity.

4. The control circuit of claim 1 wherein said current control circuit includes a triac having load electrodes connected in series with the glow discharge lamp and a control electrode, and a polarity selecting circuit connected to said control electrode for causing said triac to pass a series of pulses of one polarity during one time interval and then to pass a series of pulses of another polarity during another time interval, alternately to energize the independent electrodes of the glow discharge lamp.

5. The control circuit of claim 4 wherein said polarity selecting circuit is a free running multivibrator having an output circuit coupled to said control electrodes of said triac.

6. The control circuit of claim 5 wherein said output circuit of said free running multivibrator is coupled to said control electrode through a capacitor.

7. The control circuit of claim 1 further including means to vary the rate at which said current control circuit alternately applies said pulses of said first and second polarity.

8. The control circuit of claim 7 wherein said means is a diode connected in series with resistance and capacitance and the circuit point between said resistance and said capacitance is connected to said current control circuit to control said rate.

9. A glow lamp display device comprising, a transparent envelope, first and second electrodes positioned within said envelope, said first and second electrodes forming a display pattern, and circuit means including an oscillator, and a bidirectional current control device responsive to said oscillator for continuously energizing said first and second electrodes during one period of time when all positive polarity pulses are applied thereto and another period of time when all negative polarity pulses are applied thereto to produce the de sired visual display effect from said display pattern.

10. The glow lamp display device of claim 9 wherein said first and second electrodes are of different shape.

' 11. The glow lamp display device of claim 9 wherein said first and second electrodes produce different colors when energized. 

1. A control circuit for a glow discharge lamp having independent electrodes to be illuminated upon application thereto of a voltage of a given polarity comprising; circuit means coNnected to the glow discharge lamp for receiving and alternating current voltage and controlling which polarity of voltage of the alternating current voltage is to be applied to said glow discharge lamp, and a current control circuit connected to said circuit means and in circuit with the glow discharge lamp to control operation of said circuit means to apply to said electrodes a series of voltage pulses of a first polarity for a first time interval and then apply a series of voltage pulses of opposite polarity for a second time interval, thereby alternately visibly illuminating the electrodes of the glow discharge lamp.
 2. The control circuit of claim 1, wherein said current control circuit includes polarity selecting means to effect current conduction of a plurality of pulses of said first polarity and then current conduction of a plurality of pulses of said opposite polarity.
 3. The control circuit of claim 1 wherein said current control circuit includes first and second diodes connected in parallel and arranged for opposite conductivity, first and second switch means connected in series with said first and second diodes respectively, and polarity control circuit means connected to said first and second switch means alternates to close said first and second switch means thereby allowing passage of pulses of one polarity and then passage of pulses of another polarity.
 4. The control circuit of claim 1 wherein said current control circuit includes a triac having load electrodes connected in series with the glow discharge lamp and a control electrode, and a polarity selecting circuit connected to said control electrode for causing said triac to pass a series of pulses of one polarity during one time interval and then to pass a series of pulses of another polarity during another time interval, alternately to energize the independent electrodes of the glow discharge lamp.
 5. The control circuit of claim 4 wherein said polarity selecting circuit is a free running multivibrator having an output circuit coupled to said control electrodes of said triac.
 6. The control circuit of claim 5 wherein said output circuit of said free running multivibrator is coupled to said control electrode through a capacitor.
 7. The control circuit of claim 1 further including means to vary the rate at which said current control circuit alternately applies said pulses of said first and second polarity.
 8. The control circuit of claim 7 wherein said means is a diode connected in series with resistance and capacitance and the circuit point between said resistance and said capacitance is connected to said current control circuit to control said rate.
 9. A glow lamp display device comprising, a transparent envelope, first and second electrodes positioned within said envelope, said first and second electrodes forming a display pattern, and circuit means including an oscillator, and a bidirectional current control device responsive to said oscillator for continuously energizing said first and second electrodes during one period of time when all positive polarity pulses are applied thereto and another period of time when all negative polarity pulses are applied thereto to produce the desired visual display effect from said display pattern.
 10. The glow lamp display device of claim 9 wherein said first and second electrodes are of different shape.
 11. The glow lamp display device of claim 9 wherein said first and second electrodes produce different colors when energized. 